326 Professor Arthur W. Crossley [Feb. 5, 



group, a bluish red colour is produced, and an amino group gives a 

 violet colour. 



CO NH^ CO NHo 



OCO 000 



CO OH CO NH., 



Bluish Red Violet 



The point is further illustrated bj the following series : — 



CO NHo CO NH., 



OCO 000 



CO NH^ C0 NH.CHg 



Violet Blue Violet 



CO NH2 CO NH.CH3 



000 OCO 



CO NH.C-H; CO XH.C-H- 



Blue Greenish Blue 



CO NH.C-H- 



000 



CO NH.C-H^ 



Green 



The influence of the number and position of the substituting 

 groups is again shown by a comparison of the formulae and colours 



■of the following substances :- 



